WO2003088712A2

WO2003088712A2 - Heat exchanger provided for heating purposes and comprising an electric heating device

Info

Publication number: WO2003088712A2
Application number: PCT/EP2003/003770
Authority: WO
Inventors: Peter Englert; Michael Kohl; Matthias Traub
Original assignee: Behr Gmbh & Co.
Priority date: 2002-04-12
Filing date: 2003-04-11
Publication date: 2003-10-23
Also published as: AU2003239802A1; EP1497594A2; DE10216157A1; JP4264008B2; EP1497594B1; US20050175327A1; ATE318395T1; ES2257673T3; JP2005522666A; DE50302474D1; AU2003239802A8; WO2003088712A3

Abstract

The invention relates to a heat exchanger provided for heating purposes, particularly for a motor vehicle, comprising: a number of parallel pipes, at least one electric heating device (4), which is mounted each time between two adjacent pipes, and comprising a number of fin elements (5) situated between each pair of adjacent pipes and between each heating device (4) and the pipes adjacent thereto. In order to be able to better control the power absorption of the heating devices (4), each heating device (4) comprises two separately controllable heating sections (6, 7). One heating section (6) is placed on one side (8) of the heating device (4) facing one adjacent pipe, whereas the other heating section (7) is placed on an opposite side (9) of the heating device (4) facing the other adjacent pipe.

Description

BEHR GmbH & Co.

Mauserstrasse 3, 70469 Stuttgart

Heat exchanger with electrical heating device used for heating purposes

The present invention relates to a heat exchanger for heating purposes, in particular for a motor vehicle, with the features of the preamble of claim 1.

Such a heat exchanger is known, for example, from DE 198 35 229 A1 and has a plurality of parallel tubes and a plurality of electrical heating devices which are each arranged between two adjacent tubes. In addition, a plurality of fin elements are provided, each of which is arranged between pairs of adjacent tubes and between each heating device and the adjacent tubes. Such a heat exchanger is used, for example, in a motor vehicle in a heating circuit of an air treatment system in order to heat air that is supplied to a vehicle interior. For this purpose, the heating circuit fluid circulates in the pipes. The air to be heated flows between the tubes through the fin elements. In normal operation, the hot heating fluid transfers heat to the pipes and from them to the fin elements. The heat then reaches the air from the rib elements. In the event that sufficient heat cannot be supplied via the heating liquid, the electrical heating devices are provided which, when activated, convert electrical current into heat and emit it to the fin elements. In the known heat exchanger, each heating device contains an individual heating element, which can expediently be formed by at least one PTC element. The heating element is rarely connected to the rib elements in a heat-transferring manner on two opposite outer sides. In order to be able to ensure a sufficiently uniform heating of the air flow, several heating devices of this type are used approximately evenly between the fins of the heat exchanger. The number of these heating devices cannot be chosen arbitrarily large, since for normal operation there must be a sufficiently large number of pipes in order to be able to guarantee the necessary heat transfer to the air flow. The current requirement of the individual heating element is relatively high, so that when it is used in a motor vehicle in certain operating states of the vehicle, it is necessary to switch off one or more heating elements in order to avoid overloading the vehicle's power supply network. If several heating elements are switched off, uniform heating in the air flow can no longer be achieved, which can lead to a loss of comfort.

The present invention is concerned with the problem of specifying an improved embodiment for a heat exchanger of the type mentioned at the outset, which is easier to control, in particular, with regard to its power requirement.

According to the invention, this problem is solved by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea of equipping the individual heating devices with two heating strands which can be controlled separately and which emit their heat directly or indirectly to the rib elements on two opposite sides of the heating device. Each heating element has at least one heating element, which is preferably designed as a PTC element. Due to the structure according to the invention, it is possible with a constant number of heating devices to accommodate twice the number of heating strands in the heat exchanger. With the heating output remaining the same, the electrical output on the individual heating sections can be halved. The construction according to the invention therefore makes it possible to better adapt the connection or disconnection of individual heating strands to the current load capacity of the power network to which the heating devices are connected.

A simplified structure can be achieved in that each heating device has a tubular housing which has two mutually parallel side walls, on the outside of which the rib elements and on the inside of the heating strands are arranged to transmit heat.

In one development, each heating device can contain two pressure plates, each of which abuts one of the heating strands and is pressed apart with at least one spring element to press the heating strands against the side walls of the housing. By actively pressing the heating strands against the housing, intensive heat transfer from the heating strands to the housing can be guaranteed.

In a particularly advantageous embodiment, the housing and the pressure plates can be designed as electrical conductors; in which case the inner side of the respective pressing plate forms a first electrical connection of this heating element, while the outer side of the respective side wall of the housing forms a second electrical connection of this heating element. In addition, the two pressure plates are electrically insulated from each other.

In order to be able to electrically isolate the two electrically conductive pressure plates from one another, the following measures can be used alternatively or cumulatively:

- The spring element can be designed to be electrically insulating,

an electrical insulator can be arranged between the spring element and at least one of the pressure plates, the spring element can be equipped with an electrically insulating film, coating, painting, anodizing and / or surface at least in a contact area adjacent to the pressure plates, at least one of the pressure plates can be provided with an electrically insulating film at least in a contact area adjacent to the spring element, Coating, painting and / or surface be equipped.

Further important features and advantages of the invention result from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, the same reference numerals referring to the same or functionally identical or similar components.

Each shows schematically

Fig. 1 is a front view of an inventive

Heat exchanger,

2 is a sectional view of the heat transfer after

1 corresponding to the section lines II in Fig. 1,

Fig. 3 to 6 cross sections through different embodiments of heating devices of the heat exchanger. 1 and 2, a heat exchanger 1 according to the invention consists of a plurality of tubes 2 which are arranged parallel to one another. These tubes 2 are usually arranged next to one another in a plane which corresponds to the plane of the drawing in FIG. 1 and is denoted by 3 in FIG. 2. The tubes 2 are designed here as so-called "flat tubes" and thus have a cross section which is dimensioned transversely to the level 3 considerably larger than parallel to the level 3. The heat exchanger 1 also has several, here four, electrical heating devices 4, which are also parallel to run the tubes 2 and are each arranged between two adjacent tubes 2. Furthermore, a multiplicity of rib elements 5 are provided, the ribs of which run in such a way that they can be flowed through transversely to the plane 3. The rib elements 5 are on the one hand in each case between pairs of adjacent tubes 2. On the other hand, such rib elements 5 are each arranged between each heating device 4 and the tubes 2 adjacent to it.

The heat exchanger 1 is preferably used in an air treatment device of a motor vehicle to heat an air flow that is to be supplied to a vehicle interior as required. For this purpose, the air flow is guided across the plane 3 through the heat exchanger 1. The heat exchanger 1 is then connected to a heating circuit, so that a heating liquid circulates in the tubes 2 of the heat exchanger 1. This heating circuit can, for example, be integrated in a cooling circuit of an internal combustion engine of the vehicle. The heat transfer from the heating liquid to the air flow takes place via the tubes 2 and the fin elements 5.

In the event that the heating liquid cannot provide sufficient thermal energy, the heating devices 4 are supplied with current, corresponding current connections not being shown here.

According to FIGS. 3 to 6, each heating device 4 contains two heating lines 6 and 7, which each extend parallel to the tubes 2. Each heating section 6, 7 expediently extends along the entire length of the heating device 4, that is to say along the entire length of the tubes 2 The two heating strands 6, 7 are arranged on opposite sides 8 and 9 of the heating device 4. The arrangement and orientation of the two heating strands 6.7 is such that each heating string 6.7 faces a tube 2 adjacent to the heating device 4.

According to the invention, the two heating lines 6, 7 can be controlled or activated independently of one another.

In the embodiments shown here, the heat exchanger also has at least one tubular housing 10 which has two mutually parallel side walls 11 and 12 on the two opposite sides 8, 9 of the heating device 4. The heating lines 6, 7 are accommodated in the interior 13 of the housing 10, each heating line 6, 7 being in each case on an inside 14 or 15 of the side walls 11, 12 in a heat-transferring manner. Furthermore, these side walls 11, 12 are connected on their outside 16 and 17, respectively, to one of the rib elements 5 in a heat-transferring manner. Accordingly, there is a heat-transferring coupling of the heating strands 6, 7 via the side walls 11, 12 to the rib elements 5.

In order to press the heating strands 6, 7 to improve the heat transfer against the side walls 11, 12, two pressure plates 18 and 19 are arranged in the interior 13 of the housing 10, each on the inside 21 and 22 of the side facing away from the side wall 11, 12 the respective heating branch 6.7. In addition, a plurality of spring elements 20 can be provided, only one of which is shown in FIGS. 3 to 6 and which are arranged between the pressure plates 18, 19 and press them apart outwards. With the help of the spring elements 20, the pressure plates 18, 19 are thus pressed against the heating strands 6, 7 and the heating strands 6, 7 against the side walls 11, 12.

According to a particularly advantageous embodiment, the housing 10 and the pressure plates 18, 19 are designed as electrical conductors. In particular, the housing 10 and the pressure plates 18, 19 are made of metal. The heating strands 6.7 used are designed so that for each heating section 6, 7, the inside 21 or 22, on which the respective pressure plate 18 or 19 abuts, forms a first electrical connection of the respective heating section 6, 7. Furthermore, for each heating section 6, 7, an outer side 23 or 24, with which the respective heating section 6, 7 bears against the respective side wall 11, 12 of the housing 10, is designed as a second electrical connection of the respective heating section 6, 7.

In order to be able to supply the heating strands 6, 7 with electrical current, it is therefore sufficient to connect the pressure plates 18, 19 and the housing 10 accordingly to a power supply. Since the two heating lines 6, 7 can be controlled independently of one another for heating, it is necessary to connect the two heating lines 6, 7 independently of one another to the respective power supply. For this purpose, the two pressure plates 18, 19 must be insulated from one another.

The mutual insulation of the two pressure plates 18, 19 can be implemented in a variety of ways.

For example, according to FIG. 3, it is possible to design the spring element or elements 20 to be electrically insulating. For example, each spring element 20 consists of an electrically non-conductive material. It is also possible to electrically isolate the respective spring element 20 at least in a contact area 25 in which the spring element 20 bears on one of the two pressure plates 8, 19. This insulation can be achieved, for example, by means of an insulating film, coating, painting, anodization. It is also possible to provide this contact area 25 with an electrically insulating surface by means of anodization.

4, the desired insulation can also be achieved in that between the spring elements 20 and one of the pressure plates

18, 19 an electrical insulator 26 is arranged. Such an insulator 26 can consist, for example, of a suitable plastic or can be formed, for example, by a mica film or by glass fiber reinforced epoxy resin. According to FIGS. 3 to 5, a carrier 27 is arranged in the housing 10 for simplified positioning of the heating strands 6, 7, on which, for example, the pressure plates 18, 19 can be clipped. With the aid of such a carrier 27, the assembly of the heating devices 4 can be considerably simplified.

According to FIG. 5, in a special embodiment of this carrier 27, a partition wall 28 can be positioned so that the one pressure plate 18 bears against this partition wall 28 and the spring element 20 presses on the other hand. The material used for the carrier 27 is so elastic that the pressing force of the spring element 20 can be transmitted essentially to the pressure plate 18 abutting the partition wall 28. Furthermore, the carrier 27 is made of an electrically insulating material at least in the region of its partition 28, as a result of which the desired insulation of the two pressure plates 18, 19 from one another is achieved. In the event that the carrier 27 is made from an injection molded part made of plastic, it is expedient to inject the carrier 27 directly onto the respective pressure plate 18, at least in the region of its partition wall 28. This can also result in a simplification of the manufacture of the heating devices 4. The partition wall 28 can extend along the entire length of the pressure plate 18. It is also possible that the partition wall 28 extends as a web only in the area of the spring element 20, in which case, depending on the number of spring elements 20, a plurality of web-shaped partition walls 28 can also be provided.

6, in order to achieve the desired insulation between the two pressure plates 18, 19 in one or both pressure plates 18, 19, at least one contact area 29 in which the spring element 20 rests on the respective pressure plate 18, 19 can be provided with a suitable electrical see insulation 30 may be provided. This insulation 30 can be formed, for example, by an electrically insulating film, coating or paint. It is also possible to form the insulation 30 by means of an electrically insulating surface which has been produced by means of anodization. The coating or varnish used to produce the insulation on the respective carrier plate 18, 19 or on the respective spring element 20 can be achieved, for example, with a high-temperature resistant varnish applied in one or more layers, or by a Teflon coating or by a glass fiber coating. It is also possible to glue a high-temperature polyester film onto the respective pressure plate 18, 19 or onto the spring element 20. Furthermore, an aluminum adhesive tape can also be used which has been designed to be insulating in a suitable manner, for example by means of an electrically insulating film, coating or lacquer. In addition, the various insulation options mentioned can be combined with one another. Layer thicknesses of 10 to 500 μm are possible, but care must always be taken that the respective insulation is dimensioned such that it withstands the spring force generated by the respective spring element 20 during the entire intended life of the heat exchanger 1. The insulating coating or film is to be designed in such a way that it is not subject to thermoplastic deformability over the entire service life of the heat exchanger 1.

The integration according to the invention of two independently controllable or operable heating strands 6, 7 in a heating device 4 enables improved, in particular a relatively finely graduated, power consumption of the heating devices 4. This makes it possible to optimally utilize the available power in order to use the air if necessary. Heat the flow additionally by activating more or less heating lines 6,7. The use of heating devices 4, each of which contains two heating strands 6, 7, ensures on the one hand that existing designs of the heat exchanger 1 do not have to be changed or only slightly. On the other hand, a more uniform introduction of heat into the air flow is also achieved, even if not all heating strands 6, 7 of all heating devices 4 are active.

Each of the heating strands 6, 7 is preferably formed from at least one PTC element. A PTC element is a semiconductor which, on the one hand, emits heat when a current is applied and which on the other hand has an increasing electrical resistance with increasing heat. As a result, such a PTC element regulates itself automatically to a predetermined temperature in the event of current being applied.

LIST OF REFERENCE NUMBERS

heat exchangers

pipe

level

heater

rib element

heating section

Page of 10

casing

Sidewall of 10

Interior of 10

Inside of 11

Inside of 12

Outside of 11

Outside of 12

pressure plate

spring element

Inside of 6

Inside of 7

Outside of 6

Outside of 7

Contact area of 20

insulator

carrier

Partition of 27

Contact area of 18.19

Insulation / coating / painting / film / surface

Claims

Patent claims

1. Heat exchanger for heating purposes, in particular for a motor vehicle,

- with several parallel tubes (2),

- With at least one electric heating device (4), which is or are arranged between two adjacent pipes (2),

with a plurality of fin elements (5), each of which is arranged between pairs of adjacent tubes (2) and between each heating device (4) and the adjacent tubes (2), characterized in that

- That each heating device (4) has two separately controllable heating strands (6, 7), - the one heating strand (6) being adjacent to the one

Pipe (2) facing side (8) of the heating device (4) is arranged,

- While the other heating element (7) is arranged on an opposite, the other adjacent tube (2) facing other side (9) of the heating device (4).

2. Heat exchanger according to claim 1, characterized in that each heating device (4) is arranged in a tubular housing (10) which has two mutually parallel side walls (11, 12), on the outer sides (16, 17) of which the rib elements (5 ) are arranged to transmit heat and on the inner sides (14, 15) of the heating strands (6, 7) are arranged to transmit heat.

3. Heat exchanger according to claim 1, characterized in that each heating device (4) contains two pressure plates (18, 19), each of which abuts one of the heating strands (6, 7) and for pressing the heating strands (6, 7) against the side walls (11, 12) of the housing (10) are pressed apart with at least one spring element (20).

4. Heat exchanger according to claim 3, characterized in that - the housing (10) and the pressure plates (18, 19) are designed as electrical conductors,

- That with each heating element (6, 7), its inside (21, 22), which bears against the respective pressure plate (18, 19,), forms a first electrical connection of the heating element (6, 7), while its on the respective side wall (11, 12) of the housing (10) adjacent outer side (23, 24) forms a second electrical connection of the heating branch (6, 7),

- That the two pressure plates (18, 19) are electrically insulated from one another.

5. Heat exchanger according to claim 4, characterized in that the spring element (20) is electrically insulating.

6. Heat exchanger according to claim 4 or 5, characterized in that an electrical insulator (26) is arranged between the spring element (20) and at least one of the pressure plates (18, 19).

7. Heat exchanger according to one of claims 4 to 6, characterized in that the spring element (20) at least in one of the pressure plates (18,19) adjacent contact area (25) and / or at least one of the pressure plates (18,19) at least a contact area (29) abutting the spring element (20) with an electrical trically insulating film and / or coating and / or painting is equipped and / or has an electrically insulating surface by means of anodization.

8. Heat exchanger according to one of claims 2 to 7, characterized in that a carrier (27) for positioning the heating strands (6, 7) is arranged in the housing (10).

9. Heat exchanger according to claim 8 and at least according to claim 4, characterized in

- That the carrier (27) has at least one partition (28) on which on the one hand one of the pressure plates (18, 19) abuts and on the other hand the at least one spring element (20) presses - that the carrier (27) at least in the area its partition (28) is designed as an electrical insulator.

10. Heat exchanger according to claim 9, characterized in that the carrier (27) is an injection molded part made of plastic which is injection-molded onto the respective pressure plate (18, 19) in the region of its partition (28).

11. Heat exchanger according to one of claims 1 to 10, characterized in that each heating section (6,7) is designed as a PTC element.